A microelectronic imaging device or image sensor is generally formed by a matrix of pixels and of at least one electronic control circuit formed around the matrix. Each pixel comprises at least one photoelectric detector, for example, a photodiode or a phototransistor, provided to convert the energy of the incidental photons on the pixel into electron-hole pairs. The matrix of pixels also called the “active matrix” may be especially covered with an insulating layer and a trichromatic or three color filter formed on this insulating layer. The color filter is formed by colored filtering elements, respectively capable of filtering a range of wavelengths from the visible luminous spectrum, and may be for example of the RGB type (Red Green Blue) or for example of the CMY type (Cyan Magenta Yellow). The filtering elements may be arranged according to a Bayer pattern. The filtering elements may also be formed by blocks based on a polymer or a photosensitive resin, and made using at least one photolithographic method, during which the resin or the polymer is exposed, for example, using UV radiation through a mask. After exposure, the resin is developed. During this development, a large quantity of resin is removed from zones of the microelectronic device that are not located opposite the active matrix, with respect to a quantity of resin removed from the non active zones of the microelectronic device that are not located opposite the active matrix. This can lead to an incorrect definition of the filtering elements located at the periphery of the matrix.
To address this problem, a known method includes forming a color filter equipped with dummy filtering elements at the periphery, that are not located above and opposite the active matrix.
One specific embodiment of a microelectronic imaging device or image sensor, provides for the production of an active matrix equipped with a given number of metallic interconnection levels, for example 2 interconnection levels, and an electronic control circuit equipped with a greater number of metallic interconnection levels than the given number, for example, 4 interconnection levels. In this specific embodiment, the insulating layer that covers the active matrix and the electronic control circuit is capable of forming a cavity whose bottom is located above and opposite the active matrix. In this case especially, the formation of the color filter, and, in particular, the photolithographic method which permits the blocks of resin to be defined raises a problem in that it is difficult to obtain resin patterns with correct definition both inside and outside of the cavity at the same time. Furthermore, if one favors obtaining resin patterns with the correct definition inside of the cavity, a phenomenon of the resin outside of the cavity losing adhesion may occur.